The present invention relates to the conveyance or transportation of objects, more particularly to methods and apparatuses for controlling or regulating the operation of devices such as vertical package conveyors.
A “vertical package conveyor” (“VPC”) is a conveyance apparatus typically of a kind that includes one or more (usually, many) horizontal tray components that are physically attached to a movable chain, wherein the chain moves vertically, often on a continual basis, so as to transport bulk materials and other packages from one location (e.g., level or floor) to another. Due to their complexity and dynamism, VPCs are intrinsically dangerous, maintenance-intensive and difficult to troubleshoot.
Vertical package conveyors are used aboard some United States Navy ships. According to current Navy practice, vertical package conveyors are associated with a relay controller. A relay type of controller limits the ability to introduce new technology and intelligent sensors to a vertical package conveyance system. A system implementing a relay controller is incapable of being connected to any type of network. Some of the existing electrical components require periodic adjustments to ensure that the system remains reliable and safe. If these adjustments drift or for some reason vary, the conveyor could then have major failures and possibly become unsafe.
The U.S. Navy has customarily predicated its ship maintenance systems on time-directed preventive maintenance principles. Recently, the U.S. Navy has been transitioning in favor of “condition-based maintenance” (“CBM”) principles, with a view toward increasing readiness, decreasing maintenance and decreasing manning requirements. Generally, the objective of the U.S. Navy's transformation from time-directed preventive maintenance to condition-directed maintenance is to optimize readiness while reducing maintenance and manning requirements. The underlying concept of condition-based maintenance (synonymously referred to as “condition-directed maintenance”) is that the utilization of sensors, algorithms and automated reasoning and decision-making models to monitor equipment operations will provide critical analyses to operators that will help prevent impending failure. “Red flags” will appear to operators so that maintenance efforts can focus limited resources on areas most needed to ensure safety and mission readiness, while at the same time minimizing operating costs, labor and risk of mission-degrading failure. It is anticipated that, at optimal capacity, the U.S. Navy's CBM technology will: detect and classify impending failures; predict the remaining life cycle of equipment; interface with the control system to take action; provide support in performing corrective maintenance; provide data to life cycle management activities; and, update logistics support system. The expectation is that significant improvements in safety, reliability and affordability will ensue.
A “programmable logic controller” (“PLC”) is a specialized computer device, typically of rugged construction, that reads input signals, runs control logic, and writes output signals. PLCs have been used in industry for over thirty years for effecting “automation” such as involving the exercise of control of a system of machinery in a manner involving the turning on or off of outputs, based on a state of inputs. Typically used for monitoring important process parameters and adjusting process operations accordingly, a PLC is suitable for assembling and concentrating voluminous data (e.g., status information) that is uploaded therein in a compact form. In earlier times, electrical control was based on relays that allowed power to be switched on and off without a mechanical switch. Relays are still used to make simple logical control decisions, but PLCs are more commonly used for effecting more complicated controls. Programmable logic control typically represents a computerized version of a relay control system that can be used to control manufacturing and other systems. The programming is usually performed using “ladder logic,” involving the setting up, inter-linking and timing of sequences in a manner mimicking relay logic.
A relay type of vertical package conveyance control system does not lend itself to incorporation of the CBM philosophy recently instituted by the Navy. Some repairs have resulted in inordinate costs due to the failure of this relay-type control system to identify the degrading conditions of components. It would be desirable to practice a vertical package conveyance methodology that is consistent with CBM values.
The following U.S. patent documents, incorporated herein by reference, are pertinent to vertical package conveyors: Combs U.S. Pat. No. 6,536,582 issued 25 Mar. 2003; Grond U.S. Patent Application Publication 2002/0014392 A1 published 7 Feb. 2002; Rapell U.S. Pat. No. 6,059,521 issued 9 May 2000; Mulhern U.S. Pat. No. 5,718,322 issued 17 Feb. 1998; Grathoff U.S. Pat. No. 5,320,471 issued 14 Jun. 1994; Franke U.S. Pat. No. 5,350,050 issued 27 Sep. 1994; Pfleger U.S. Pat. No. 5,205,379 issued 27 Apr. 1993; Splitstoser et al. U.S. Pat. No. 4,986,411 issued Jan. 22, 1991; Freeman U.S. Pat. No. 4,219,301 issued 26 Aug. 1980; Eklof et al. U.S. Pat. No. 4,020,953 issued 3 May 1977; Henkel U.S. Pat. No. 3,972,412 issued 3 Aug. 1976.